Integrated optimization of timetabling and electric multiple unit (EMU) circulation on a new connecting line to the high-speed railway (HSR) network

This study optimizes train timetables and electric multiple unit (EMU) circulation plans for the newly built high-speed railway (HSR) connecting line, addressing the challenge of integrating new infrastructure into existing networks without disrupting current operations. We propose an integer linear programming model that joins timetabling and EMU circulation planning by generating candidate train sets (extended and cross-line trains) and incorporating flow, time, and spatial demand constraints. Validated on a real-world connecting line in the Yangtze River Delta, China, the model reduces EMU usage by 2.17% and total connection time by 5.02% compared to manual planning while fully meeting travel demands. Sensitivity analyses highlight dynamic trade-offs between demand fluctuations, station capacities, and resource efficiency. The framework provides a scalable tool for the cost-effective commissioning of new lines.